Relative atomic mass - A r. Just another way of saying how heavy different atoms are compared with the mass of one atom of carbon – 12 (regular carbon!). Mass number. Atomic number. Q. What does the atomic mass number represent?. Number of protons present.
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Just another way of saying how heavy different atoms are compared with the mass of one atom of carbon – 12 (regular carbon!)
Q. What does the atomic mass number represent?
Number of protons present
A. Total number of protons and neutrons found in an atoms nucleus
You can work out how many neutrons an element has by subtracting the proton number from the mass number!!
So how many neutrons:
Relative atomic mass is easy!! It’s the same value as the mass number – it just sounds scarier!
So what does this tell us about Mg and H?
Table.1. Different elements and their different Ar
Example 1: Find the Mr of carbon monoxide (CO).
The Ar of carbon is 12 and the Ar of oxygen is 16.
So the Mr of carbon monoxide is 12 + 16 = 28.
So the Mr of sodium oxide is (23 x 2) + 16 = 62.
Sulphur dioxide SO2
Calcium carbonate CaCO3
Sodium hydroxide NaOH
Sulphuric acid H2SO4
Hydrochloric acid HCl
Copper sulphate CuSO4
Magnesium chloride MgCl2
Sodium carbonate Na2CO3
avg. of allisotopes that exist in nature.
Average Mass of Isotopes
- abundance of isotope is just as important as mass!
Natural copper (Cu) consists of 2 isotopes ...
Copper - 63 (mass = 62 .930 g/mole)
Copper - 65 (mass = 64 .930 g/mole)
mass x abundance for each isotope
Step 1 :
add the two values from step 1 together
Step 2 :
62 .93 x .69 =
64 .93 x .31 =
that is mostplentiful in nature.
Oxygen-16 is the isotope that is most abundant in nature.
Three isotopes of Oxygen:
Oxygen - 16
99 . 759%
Oxygen - 17
Oxygen - 18
Read page 17 to 18 of your text and make short notes.